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#include <kern/pmap.h>
#include <inc/string.h>
#include <inc/x86.h>
#include <kern/picirq.h>

volatile void *bar_va;

int rx_buffer_ptr = 0;
int tx_buffer_ptr = 0;                 // pointers to transmit/receive buffers

const int buffer_size = 1518;          // length of each packet buffer
int rx_buffer_count = 128;
int tx_buffer_count = 8;

const int de_size = 16;                // length of descriptor entry

uint8_t rdes[16*128];                         // pointer to ring buffer of receive DEs
uint8_t tdes[16*8];                         // pointer to ring buffer of transmit DEs

uint8_t rx_buffers[1518*128];                   // physical address of actual receive buffers (< 4 GiB)
uint8_t tx_buffers[1518*8];                   // physical address of actual transmit buffers (< 4 GiB)

uint32_t E1000_MAC[6] = {0x52, 0x54, 0x00, 0x12, 0x34, 0x56};

uint8_t manager[6000];


// does the driver own the particular buffer?
int driverOwns(uint8_t *des, int idx)
{
    return (des[de_size * idx + 7] & 0x80) == 0;
}

// get the next transmit buffer index
int nextTxIdx(int cur_tx_idx)
{
    int ret = cur_tx_idx + 1;
    if(ret == tx_buffer_count)
        ret = 0;
    return ret;
}

// get the next receive buffer index
int nextRxIdx(int cur_rx_idx)
{
    int ret = cur_rx_idx + 1;
    if(ret == rx_buffer_count)
        ret = 0;
    return ret;
}

// initialize a DE
void initDE(uint8_t *des, int idx, int is_tx)
{
    memset(&des[idx * de_size], 0, de_size);

    // first 4 bytes are the physical address of the actual buffer
    uint32_t buf_addr = rx_buffers;
    if(is_tx)
        buf_addr = tx_buffers;
    *(uint32_t *)&des[idx * de_size] =PADDR( buf_addr + idx * buffer_size);

    // next 2 bytes are 0xf000 OR'd with the first 12 bits of the 2s complement of the length
    uint16_t bcnt = (uint16_t)(-buffer_size);
    bcnt &= 0x0fff;
    bcnt |= 0xf000;
    *(uint16_t *)&des[idx * de_size + 4] = bcnt;

    // finally, set ownership bit - transmit buffers are owned by us, receive buffers by the card
    if(!is_tx)
        des[idx * de_size + 7] = 0x80;
}

void writeRAP32(uint32_t val)
{
    outl(E1000REG(0x14), val);
}

void writeRAP16(uint16_t val)
{
   outw(E1000REG(0x12), val);   
}

uint32_t readCSR32(uint32_t csr_no)
{
   writeRAP32(csr_no);
   return inl(E1000REG(0x10));
}

uint16_t readCSR16(uint16_t csr_no)
{
     writeRAP16(csr_no);
     return inw(E1000REG(0x10));
}

void writeCSR32(uint32_t csr_no, uint32_t val)
{
    writeRAP32(csr_no);
    outl(E1000REG(0x10), val);
}

void writeCSR16(uint16_t csr_no, uint16_t val)
{
    writeRAP16(csr_no);
    outw(E1000REG(0x10), val);
}

void Reset()
{
     uint32_t a = *(  (uint32_t*)E1000REG(0x18));
     uint16_t b = *(  (uint16_t*)E1000REG(0x14));
     int i = 0;

     while(i<16000000)
     {
        i++;
     }

    writeCSR32(0, 0);
    uint32_t csr58 = readCSR32(58);
    csr58 &= 0xFF00;  // SWSTYLE is 8 bits (7:0)
    csr58 |= 2;
    writeCSR32(58, csr58);

    uint32_t bcr2 = inl(E1000REG(0x1c));

    bcr2 |= 2;
    writeRAP32(58);
   
    outl(E1000REG(0x1c), csr58);

}


static void am79c973_init()
{

        uint8_t l = 3;
        uint8_t l2 = 7;
     
        *(manager+3) = l<<4; //tr len
        *(manager+2) = l2<<4; //rx  len
        *((uint16_t*)manager)=0x0000;
        *(manager+4)=E1000_MAC[0];
        *(manager+5)=E1000_MAC[1];
        *(manager+6)=E1000_MAC[2];
        *(manager+7)=E1000_MAC[3];
        *(manager+8)=E1000_MAC[4];
        *(manager+9)=E1000_MAC[5];
        *(manager+10)=0;
        *(manager+11)=0;
        *(manager+12)=0;
        *(manager+13)=0;
        *(manager+14)=0;
        *(manager+15)=0;
        *(manager+16)=0;
        *(manager+17)=0;
        *(manager+18)=0;
        *(manager+19)=0;
        *((uint32_t*)(manager+20))=PADDR(rdes);  // descriptor phys addr
        *((uint32_t*)(manager+24))=PADDR(tdes);

        rx_buffer_ptr = 0;
        tx_buffer_ptr = 0;
        int i;

        //init descriptors
        for( i = 0; i < 8; i++)
        {
            initDE(tdes, i, 1);
        }

        for( i = 0; i < 128; i++)
        {
            initDE(rdes, i, 0);       
        }
        // write init structure addr
       writeCSR32 (1, PADDR(manager) & 0xFFFF );
       writeCSR32 (2, (PADDR(manager) >> 16) & 0xFFFF );


        // disable interrupts
       uint32_t csr3 =readCSR32(3);
       csr3 |= 1UL << 10;
       csr3 |= 1UL << 8;
       csr3 |= 1UL << 9;
       writeCSR32(3, csr3);

       // begin inititalization
      uint32_t st = readCSR32(0);
       //set   
       st |= 1UL << 0;
       writeCSR32(0, st);
       // wait for complete
       do{
        st = readCSR32(0);
       } while(!(st&(1UL << 8)));

    // start the board
    st = readCSR32(0);
    st |= 1UL << 1;
    writeCSR32(0, st);
}


int e1000_attachfn(struct pci_func *pcif)
{
   pci_func_enable(pcif);
   cprintf("reg_base:%x, reg_size:%x\n", pcif->reg_base[0], pcif->reg_size[0]);
         
   //Exercise4 create virtual memory mapping
   bar_va =pcif->reg_base[0];
    Reset();
   am79c973_init();
   
   return 0;
}

int e1000_transmit(void *buffer, size_t size)
{   
    if(!driverOwns(tdes, tx_buffer_ptr))
    {
         return -E_TRANSMIT_RETRY;
    }
 
    memcpy((void *)(tx_buffers + tx_buffer_ptr * buffer_size), buffer, size);

    tdes[tx_buffer_ptr * de_size + 7] |= 0x2;

    tdes[tx_buffer_ptr * de_size + 7] |= 0x1;

    uint16_t bcnt = (uint16_t)(-size);
    bcnt &= 0xfff;
    bcnt |= 0xf000;
    *(uint16_t *)&tdes[tx_buffer_ptr * de_size + 4] = bcnt;

    // finally, flip the ownership bit back to the card
    tdes[tx_buffer_ptr * de_size + 7] |= 0x80;

    // update the next transmit pointer
    tx_buffer_ptr = nextTxIdx(tx_buffer_ptr);

    return 0;
}

int e1000_receive(void *addr, size_t *len)
{     
    *len =0;
    int ret = -E_RECEIVE_RETRY;
    char* shiftedAddr = addr;

    while(driverOwns(rdes, rx_buffer_ptr))
    {
        // packet length is given by bytes 8 and 9 of the descriptor
        //  (no need to negate it unlike BCNT above)
        uint16_t plen = *(uint16_t *)&rdes[rx_buffer_ptr * de_size + 8];

        // the packet itself is written somewhere in the receive buffer
        void *pbuf = (void *)(rx_buffers + rx_buffer_ptr * buffer_size);

        memcpy(shiftedAddr, pbuf, plen);
        *len+=plen;
        shiftedAddr+=plen;

        // hand the buffer back to the card
        rdes[rx_buffer_ptr * de_size + 7] = 0x80;

        // increment rx_buffer_ptr;
        rx_buffer_ptr = nextRxIdx(rx_buffer_ptr);
        ret =0;
    }

    return ret;
       
}